Dr Amara Jambai, the director of disease prevention and control at Sierra Leone's health ministry, told the BBC that staff at the clinic in Koindu town in eastern Sierra Leone had tried to stop the six patients from being removed.

However, the families had been "aggressive" as they took their relatives away, he said.

The BBC's international development correspondent Mark Doyle says while it is unclear why relatives did this, a Sierra Leonean official speculated that it was because they thought their loved ones would die in the clinic or on transfer to a hospital in Kenema, the main city in the region.

Four of the six had already tested positive for Ebola, and one them had died after being removed from the clinic, Dr Jambai said.

The authorities did not know where the others were and were now very concerned they could spread the disease, he added.

Dr Jambai said two people had so far died of Ebola in Sierra Leone, and not four as previously reported.

Guinea has been worst-affected, with 258 suspected and confirmed cases of Ebola, including 174 deaths - 146 of which have been laboratory-confirmed positive.

In Liberia there have been 12 suspected cases, with nine deaths.

A spokesman for the World Health Organisation (WHO) in Geneva said Ebola was often spread when family members, trying to care for a relative, came into contact with infected body fluids.

The WHO says treatment by qualified personnel can sometimes help patients and reduces the risk of outbreaks spreading.